Gliosis specimens contain clonal cytogenetic abnormalities

The relevance of sex chromosome aneusomy and trisomy 7 in neoplastic brain tissue is controversial. For better understanding of the relative importance of these anomalies, we made a conventional cytogenetic study of cells from tissue obtained from patients who underwent partial cerebral resection for a seizure disorder. Each specimen exhibited “gliosis,” but none contained histologically identifiable tumor cells. Sixty-six specimens were analyzed by routine cytogenetic methods. Nonclonal abnormalities were observed in 11.6% of the cells (86% of cases) analyzed. In 11 cases, however, simple clonal karyotypes were observed. Of these cases, six involved loss of a Y chromosome and three involved loss of an X chromosome. Among the cases with loss of an X chromosome, two exhibited multiple abnormal clones. One of these cases had trisomy 7 as well as trisomy 18, and another had a supernumerary psu dic(15)(q13). The supernumerary chromosome was constitutional. One patient had possible Klinefelter syndrome. An additional case had a clonal del(10)(q23) that may have resulted from a hereditary fragile site. We conclude that although some of the apparently acquired clonal and nonclonal abnormalities may be due to a consistent in vitro artifact, it is probable that they are present in the brain tissue itself. Whatever the cause, caution should be used in interpretating cytogenetic abnormalities observed in brain tumor specimens.